Thermoelectric overheat indicator

ABSTRACT

An indicating device constructed as a switch that is adapted to fit into the block of an internal combustion engine and, in operation therein, will provide a signal relative to engine overheat. More particularly, this switch operates by expansion and contraction of a microcrystalline wax in accordance with temperature changes. The wax acts upon a generally tubular elastomeric diaphragm having a thin wall lower portion and a substantially thicker walled upper portion to collapse or pinch the diaphragm at the thin wall lower portion to close a set of contacts. When the wax contracts or returns to its original state, the diaphragm follows and also returns to its initial position and configuration.

United States Patent Lynn S. Brock 12/1967 Erwin et al.......... 337/380X 73/368.3 X

[72] Inventor 9/1964 Daly et Williamsvllle, N.Y.

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[541 THERMOELECTRIC OVERHEAT INDICATOR ABSTRACT: An indicating device constructed as a switch 3 Claims 2 Drawing Figs that is adapted to fit into the block of an internal combustion 3 7/393, engine and, in operation therein, will provide a signal relative to engine overheat. More particularly, this switc expansion and contraction of a microc cordance with temperature chan h operates by generally tubular elastomeric dia lower portion and a substantially to collapse or pinch the diaphragm at the thin w tion to close a set of contacts. When the wax contrac returns to its original state, the diaphragm follows and also returns to its initial position and configuration.

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3,529,272 9/1970 Johnsonetal................ 337/380 THERMOELECTRIC OVERHEAT INDICATOR The switch is a normally open device that closes upon reaching a predetermined temperature by means of a wax material acting upon a diaphragm. The prior art, US. Pat. No. 3,308,668, shows a temperature-responsive actuator device that moves a rod in a given direction in response to a wax material acting on a diaphragm. The contacts of the switch or actuator of the present invention are incorporated directly in the body of the switch and are closed and opened through action of the wax acting to expand and contract the diaphragm in relation to temperature change. Prior art US. Pat. No. 3,359,388 shows a control device having a diaphragm therein to open the normally closed contacts by fluid passing through an orifice and acting directly on the diaphragm, as distinguished from the operation of the present invention.

This invention overcomes limitations in the prior art in that the contacts are within a main body and are located or positioned between a wax material and diaphragm on one side, and a rigid wedge-shaped or tapered plastic separator and support on the other side so as to provide adequate protection against breakage. The separator between the contacts eliminates the possibility of excessive bending or permanent deformation of the contacts during operation due to excess pressure by the diaphragm, as well as insures a quick break of the contacts. A rapid make or closing of the contacts is assured through rapid expansion of the wax, eliminating the creep condition that generally creates contact burning.

F IG. 1 shows a longitudinal view of the invention having the contacts open; and

FIG. 2 shows a partial longitudinal section view of the invention with the contacts closed.

Referring to the drawing in detail, the switch apparatus of this invention comprises a capsule or housing member generally cup-shaped and having a threaded body 12 and a headed end 14 that permits the housing to be threaded into the block or other areas of an internal combustion engine or installed in any application requiring a temperature sensing device to provide a signal to a warning device, such as a light or gauge to indicate an overheat condition. At the end opposite that of the headed end and joining the threaded body is a generally U shaped bulbous nonthreaded portion 16 that is constructed to fit in the stream of the fluid to be monitored. It is understood that bulbous end 16 may be of any convenient shape. However, the bulbous end should be constructed and formed from a material that will readily permit the desired and necessary heat transfer to the interior of the housing.

Within the housing there is provided a microcrystalline wax material 18 that is in contact with the bulbous end portion 16 and the threaded body portion 12. Adjacent to the wax material and in contact therewith is a tubular-shaped resilient elastomeric, i.e., rubber, diaphragm 20 closed at one end and having a thin wall portion or section, and a thick wall portion or section, with the thin wall section being adjacent the electrical contacts. The diaphragm is located adjacent the contacts to preclude any time delay in movement of the contacts when they are closed by action of the wax on the diaphragm. The diaphragm is held in position in the housing by action of a crimped or tumed-over portion 24 on the housing that exerts pressure on insulating member 22, flange member 26 formed on diaphragm 20, and the shoulder portion 28 formed in threaded body 12. At the center of the housing there is located a set of terminals 30, 32, with terminal 30 being the hot terminal and terminal 32 being connected to ground through housing 10. The terminals are an extension of resilient arms 34, 36 that have a pair of contacts 38, 40 on the opposite end. Between resilient arms 34, 36 is a tapered separator member 42 wherein the taper beings at 43 and terminates substantially at a point 45 adjacent contacts 38, 40. The smooth-tapered shape of separator 42 reduces the chance of permanent deformation of the resilient arms and contacts due to excess pressure that might be applied by the diaphragm by providing a space for the resilient arms to flex into. The inward flexing of resilient arms 34, 36 aids the opening of the contact members due to spring action of arms 34, 36 when the force exerted by the diaphragm is relieved.

In operation, as the temperature to be monitored rises, wax l8 expands against diaphragm 20 to pinch the diaphragm inwardly toward resilient arms 34, 36 and contacts 38, 40. Upon reaching the temperature to be detected or monitored, continued preferential pinching or collapsing of the diaphragm by the wax acts to close contacts 38, 40. The desired temperature is determined by the wax used and the heat transfer characteristics of the bulbous area. Internal pressures are kept to a minimum by use of the preferentially collapsible diaphragm which through varying wall thickness causes contact to be made initially at the ends of the terminals. As the temperature continues to rise beyond the temperature required to pinch the diaphragm to close the contacts, excess pressure on the diaphragm due to continued melting of the wax collapses the upper thick wall portion 44 of the diaphragm, creating little increase in internal pressure on the contacts and absorbs any further expansion due to further temperature rise.

As illustrated in FIG. 2, the switch is in the closed position, and it is readily seen that resilient arms 34, 36 generally follow the separator member 42 to its end, wherein contacts 38, 40 are closed to provide a signal to a light-type monitor or gauge or other signal device to provide an indication that the temperature of the fluid being monitored has reached a certain temperature, generally an overheated temperature condition. As explained earlier, diaphragm 20 is thickened in area 44 to aid separator 42 in taking up excess pressure exerted on the resilient arms by the expansion of the wax.

As is readily understood, as the wax cools because of removal of excessive heat on the switch, the pinched resilient diaphragm moves outwardly and returns to its original position and shape by following the contraction of the wax. Pressure from the resilient arms is therefore relieved to allow the contacts to open to remove the signal from the indicating device to show the overheat condition has been relieved and a normal temperature condition has been attained.

l with it to be understood that I do notdesire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

What is claimed is:

l. A switch for detecting an overheat condition comprising a housing, said housing having means of attaching said switch to the area in which an overheat condition is to be detected,

resilient arms located within said housing having contact means on one end, and terminals on the other end, a separator member between said resilient arms to maintain said contacts in a normally open position, a tubular resilient diaphragm disposed within said housing about said resilient arms, and a heat sensitive means within said housing adjacent the interior wall thereof and in engagement with said resilient member whereby said heat sensitive means expands at a given overheat condition, to pinch said tubular diaphragm member about said resilient arms to close the contacts and provide a signal relative to the temperature overheat condition.

2. In an overheat detection switch, the combination comprising a housing having means thereon for attachment to the device to be instrumented, said housing having a headed end and a forward end, a pair of resilient anns having contacts at one end that extend into the forward end of said housing, a separator member between said resilient arms to maintain said contacts in a normally open position, a flexible diaphragm disposed in said housing surrounding said resilient arms, with one section of the diaphragm being substantially thinner than the remaining section, expandable wax means also within said housing and surrounding said diaphragm and being in engagement therewith and terminal means at the end opposite said contacts whereby as said forward end is heated said wax means expands against said diaphragm to preferentially pinch the thin portion of said diaphragm to rapidly close the contacts to provide an indication of temperature overheat in the engine.

3. In a switch adapted for use in an internal combustion engine cooling system for detecting an overheat condition of the cooling fluid, the combination comprising a housing having a headed end, a threaded central body portion to attach said switch to said internal combustion engine, and an end opposite said headed end, the end opposite said headed end being adapted to be in contact with the cooling fluid of the internal combustion engine, a pair of resilient arms having contacts thereon within said housing and extending toward the fluid contacting end, a tapered separator member within said housing between said resilient arms to maintain said contacts in an open position, a flexible diaphragm disposed within said housing that surrounds said resilient arms and is in contact therewith at a point adjacent to said contacts, to preclude any time delay in the closing of the contacts, the section of said diaphragm adjacent said contacts being substantially thinner than the remaining section of the diaphragm, expandable wax means also within said housing located between the interior wall of said housing and said first expandable member and which surrounds said first expandable member, and tenninals on said resilient arms opposite said contact means for connection to a remote readout means, whereby as said expandable wax means is heated due to an engine overheat condition, it expands against said diaphragm to preferentially pinch the thin section of said diaphragm toward said resilient arms to rapidly close said contacts and provide a signal to said remote readout means to indicate an engine overheat condition, said tapered separator member serving to support said resilient arms when being pinched by said resilient diaphragm to preclude overstressing of the arms.

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1. A switch for detecting an overheat condition comprising a housing, said housing having means of attaching said switch to the area in which an overheat condition is to be detected, resilient arms located within said housing having contact means on one end, and terminals on the other end, a separator member between said resilient arms to maintain said contacts in a normally open position, a tubular resilient diaphragm disposed within said housing about said resilient arms, and a heat sensitive means within said housing adjacent the interior wall thereof and in engagement with said resilient member whereby said heat sensitive means expands at a given overheat condition, to pinch said tubular diaphragm member about said resilient arms to close the contacts and provide a signal relative to the temperature overheat condition.
 2. In an overheat detection switch, the combination comprising a housing having means thereon for attachment to the device to be instrumented, said housing having a headed end and a forward end, a pair of resilient arms having contacts at one end that extend into the forward end of said housing, a separator member between said resilient arms to maintain said contacts in a normally open position, a flexible diaphragm disposed in said housing surrounding said resilient arms, with one section of the diaphragm being substantially thinner than the remaining section, expandable wax means also within said housing and surrounding said diaphragm and being in engagement therewith and terminal means at the end opposite said contacts whereby as said forward end is heated said wax means expands against said diaphragm to preferentially pinch the thin portion of said diaphragm to rapidly close the contacts to provide an indication of temperature overheat in the engine.
 3. In a switch adapted for use in an internal combustion engine cooling system for detecting an overheat condition of the cooling fluid, the combination comprising a housing having a headed end, a threaded central body portion to attach said switch to said internal combustion engine, and an end opposite said headed end, the end opposite said headed end being adapted to be in contact with the cooling fluid of the internal combustion engine, a pair of resilient arms having contacts thereon within said housing and extending toward the fluid contacting end, a tapered separator member within said housing between said resilient arms to maintain said contacts in an open position, a flexible diaphragm disposed within said housing that surrounds said resilient arms and is in contact therewith at a point adjacent to said contacts, to preclude any time delay in the closing of the contacts, the section of said diaphragm adjacent said contacts being substantially thinner than the remaining section of the diaphragm, expandable wax means also within said housing located between the interior wall of said housing and said first expandable member and which surrounds said first expandable member, and terminals on said resilient arms opposite said contact means for connection to a remote readout means, whereby as said expandable wax means is heated due to an engine overheat condition, it expands against said diaphragm to preferentially pinch the thin section of said diaphragm toward said resilient arms to rapidly close said contacts and provide a signal to said remote readout means to indicate an engine overheat condition, said tapered separator member serving to support said resilient arms when being pinched by said resilient diaphragm to preclude overstressing of the arms. 